Adjustable length coaxial transmission line



J. L. CLARK ADJUSTABLE LENGTH COAXIAL TRANSMISSIONr LINE sept., 12, 195oFiled Nov. 27, 1945 nvm-vwo@A `JAMES l.. CLARK Patented Sept. 12, .1950

James =L. lClark,l Cambridge, Mass., assigner to the United States ofAmerica as represcntedvby the Secretary of War Application November 27,1945,.seria1fN0.-c31,1s2 7 This invention relates generallyto electricalapparatus and more particularly to coaxial transmission lines.

Often it is desirable to tune a coaxial transmission line by means of anassociated coaxial transmission line` having an adjustable shortingplunger. `Such a tuning stub having a movable shortng plunger is usuallyarranged to permit the excursion of the shorting plunger to extendsubstantially the entire length of the coaxial transmission line tuningstub.

Such a required excursion of the shorting plunger is often mechanicallyundesirable.

The required excursion of such a shorting plunger can be substantiallyreduced by having the coaxial transmission line tuning stub adjuste ablein length.

It is an object of the present invention to pro- Vide an adjustablelength coaxial line.

More specically it is an object of the present invention to provide ameans for changing the effectvie length of a coaxial transmission linewhose overall dimension is determined by stacking several lines togetherand connecting the desired lengths by the use of a switching end plug.

`Several coaxial lines of different lengths are stacked together and atone end all lines terminate in a common plane which is at right anglesto the longitudinal axes of the lines. At that end of the coaxialtransmission lines there is provided a switching plug having terminalswhich connect together two or more lines, the total length of theseconnected lines being equal to the desired total length of line.

Other objects, features and advantages of this invention will suggestthemselves to those skilled in the art and will become apparent from thefollowing description of the invention taken in connection with theaccompanying drawings in which:

Fig. 1 is an elevation of a device embodying the principles of thisinvention;

Fig. 2 is a side view of Fig. l

Fig. 3 is an elevation of a switching plug associated with the deviceshown in Figs. 1 and 2;

Fig. 4 is a side view of Fig. 3;

Fig. 5 is a schematic representation of the electrical circuit obtainedby the use of the devices shown in Figs. 1, 2, 3, and 4; and

Fig. 6 is a schematic representation of an alternate electrical circuitobtained by the use of the devices shown in Figs. 1, 2, 3, and 4.

Referring now to Figs. 1 and 2, a framework IIl has four holes bored toreceive and hold four 3 Claims. (Cl. 17E-44) coaxial transmission linesI I, I2, I3 and I4. Co- 55 i 2 l axial transmission lines II, I2, I3,an`d' I 4 terminate in a common plane determined by a' face of frameworkI0, o

' llt should be noted that the portions II and I2 formed froma'singlelength of line 22, terminate in framework I 0, and that coaxialtransmission line I4 has a movable shorting plunger I5. Coaxialtransmission line I3 is characterized by an inductive coupling loop IBwhich is formed from the inner conductor of that line where that. innerconductor breaks the confinement of its associated outer conductor. I

Referring now to Figs. 3 and 4, a switching plugl I'I has four terminalsI8, I9, 20 and 2I,l respec tively, with terminals I8 and I9 electricallycon-- nected 'and terminals 20 and 2l electrically connected. TerminalsI8, I9, 20 and v2I are disposed at f-degree intervals about thecircumference of a circle whose center coincides with the center of aface of switching plug I1.

In Figs. 1 and 2 coaxial transmission lines 22, I3, and I4 are similarlydisposed in `framework I0 and the hollow inner conductors receive andmake contact with the terminals of switching plug I'I of Figs. 3 and 4.

Fig. 5 shows the resulting circuit when switching plug II is inserted inframework I 0 such that terminals 20 and 2l connect together the innerconductors of coaxial transmission lines I3 and I4.

Fig. 6 shows the resulting circuit when switching plug I'I is rotated 90degrees from the position assumed in the above paragraph. Under theseconditions, terminals I8 and I9 of switching plug II connect togetherthe inner conductors of coaxial transmission lines 22 and I3 andterminals 20 and 2| of switching plug II connect together the innerconductors of coaxial transmission lines 22 and I4.

The apparatus shown in the drawings which embodies the principles of theinvention herein disclosed is a means for extracting radio frequencyenergy from an open line type oscillator tank circuit and thepresentation of that energy to an antenna or other load. For example,radio frequency energy may be coupled from a given source by means ofcoupling loop I 6 of line I3 and transmitted to any load (not shown)connected to one end of line I3. Lines 22 and I4 are connected to theother end of line I3 by means of a switching plug I'I, resulting in thecircuit shown in Fig. 6. An alternate interconnection made possible byrotating switching plug I1 90 degrees, results in the circuit shown inFig. 5 in which line I4 only is connected to line I3.

Under the latter conditions, line 22 forms no part of the operatingcircuit.

Depending upon the frequency o operation, either of the two aboveconnections may be made by switching plug I1 and line I3 can be tuned byadjusting shorting plunger I5 in line I 4.

The ability to remove or add line 22 to the operating circuit by thesimple method of removing switching plug I'I, rotating it 90 degrees,and then reinserting it, provides a means for effectivelyr changing thelength of the tuning line associated with line I3.. Accordingly, therequired excursions of shorting plunger I5 in line I 4 to accomplishtuning are substantially reduced even though the operating frequencyrange of the device is quite large.

It will be apparent that'there may be .deviations from the invention asdescribed Which still vention.

Accordingly I claim all such deviations which.

fall fairly Within the spirit and scope of the invention as identied inthe hereinafter appended claims.

What is claimed is:

1. An adjustable length coaxial line comprising a first coaxialtransmission line. having an inner conductor and an outer conductor,means at one end for connecting said line to a load, means at anintermediate position along said line for connecting said line to agenerator, a second coaxial transmission line having an inner conductorand an outer conductor, a movable shortingplunger in said second line, athird coaxial transmission line having an inner conductor and an outerconductor bent in a' generally U shape, said ylines being vstackedtogether with the endv of :said klines terminating in a common plane atright angles to thelongitudinal axes of said lines, and. lmeansincluding a switching plughaving four'terminals with pairs of saidterminals electrically .connected for making thedesired-interconnections .between .I

the inner conductors of said lines,v whereby vthe .4 effective length ofsaid first coaxial transmission line is altered.

2. A n adjustable length coaxial line comprising a, rst coaxialtransmission line having an inner conductor and an outer conductor,means at one end for connecting said line to a load, means at anintermediate position; along said line for. connecting said; linetoa'generator, a second coaxial transmission line having an innerconductor and an outer conductor, a movable snorting plunger in saidsecond lineI a third coaxial transmission line having an inner conductorand an outer conductor bent in a generally U shape.. and means includinga switching plug'having four terminals with pairs of said terminalselectrically connected for making the desired .interconnections betweenthe inner conductors of said lines, whereby the effective length ofsaid'iirst coaxial transmission line is altered.

3. An adjustable length coaxial line comprising a plurality ofcoaxial.transmission.line.s, each of said lineshaving an innerconductor., said lines being stacked in such a manner that an end ofeach of'said lines terminates in a common plane, .and means including aswitching plugv having a plurality of terminals, said tern1i` nalselectrically connected in pairs for interconenecting the .innerconductors of said lines, whereby the eiective length .0f said coaxialtransmission lines is altered. y

JAMES L. CLARK.

REFERENCES CITEDy The following references are of record in the leof'this Vpatent:

y UNITED STATES PATENTS Kline Apr. 8,3 1947

